No Slide Title by HC111211081323

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									Endo-Exo Convention
1) the position of double bonds relative to rings
in carbocyclic systems;
2) the relative orientation of substituents of
bridged carbocycles;
3) opposing pathways for certain intramolecular
cyclization and cleavage reactions;
4) opposing pathways for Diels-Alder type
cycloaddition reactions based on the
orientation of dienes to dieneophiles.
Alkene Orientations


                   endocyclic   exocyclic


Ring Bridging
1)   a   bridge containing a heteroatom or atoms
2)   a   shorter bridge
3)   a   saturated bridge
4)   a   less substituted bridge
5)   a   bridge with the lowest CIP priority substituents
W          W      W              W

                                        CH 3
                  O
                                        CH 3
       O
endo       exo    exo            exo

W          W      W              W

                            HO          CH 3
                  O


endo       endo       exo        endo
INTRAMOLECULAR CYCLIZATIONS

                    endocyclic addition




                   exocyclic addition
Example 1.       Endocyclic and exocyclic double bonds:
In the compound chamigrene, which was stereoselectively
synthesized by transannular cyclopropanation followed by
ring fragmentation, there is both an endocyclic double
bond and an exocyclic double bond
Example 2.       2,6-Dimethylbicyclo[3.3.1]nona-3,7-
diene-endo-2,endo-6-diol. The short bridge takes
precedence over the unsaturated bridges




                                CH 3
            H3C
                                    OH
         HO
For each bridged compound below, identify the
reference bridge and specify the endo/exo orientation
of "W" substituent

                           NH
                W
                                                                  H3C
                                                           W                      W
                                NH2     O
                         (a)                      (b)
                                                                         (c)
                                                                                  W
                Br                            W
          OEt                                             CH 3
                               O   W
                                                                   H3C
                         (d)           H3C        (e) CH 3                  (f)       CH 3

                    HO                            W


            W                      COOH                                           O

                                       H3CO                  OH     W
                         (g)                        (h)                   (i)

								
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